双螺杆挤出机内非牛顿粘性流场计算及其挤出行为研究

本文首先根据相对运动原理对双螺杆啮合几何学进行了全面、系统的研究，得出了螺杆各几何参数之间的相互关系以及螺杆各截面几何形状的解析表达式，推导出了螺杆各特征面积及体积的计算公式，讨论了它们同螺杆几何参数之间的关系，进而从几何学角度提出了螺杆各段几何参数的设计准则。本文还比较了理论结果和测绘结果，证明了本文提出的双螺杆啮合几何学理论的可靠性。

   针对双螺杆挤出机内流动介质的特殊流动特性和流动区域的复杂性，本文在分析指出传统的压力——速度有限元法在解这类流场时的不足之后，首次提出用新型的罚函数有限元法及国际上发展不久的边界元法来求解双螺杆挤出机内的流场。对非线性问题也提出了自己的处理方法，并证明了上述方法在解复杂流场问题时具有经济、方便、高效、通用、可靠等优点。

   本文对同向旋转双螺杆挤出机计量段及排气段内的流场建立了迄今为止最接近实际情况的物理模型和数学模型，并利用上述新方法在微机上对计量段及排气段内非牛顿、不等温、且含三个方向速度的粘性流场进行了计算。此后，在流场计算结果的基础上，对计量段、排气段重要的工作特性参数进行了计算、分析和讨论，进而对工艺参数和螺杆几何参数提出了选择及设计的原则，对生产中出现的问题（如排气口冒料及如何改善排气效果、抑制工作特性参数的波动等）提出了解决途径。

   本文根据流场相似条件对同向旋转双螺杆挤出机计量段的螺杆几何参数及机器工艺参数提出了相似设计方法。

   本人曾在实验室及工厂作了大量实验，文中分析比较了理论计算值及实验结果，证明了本文提出的模型合理、计算方法先进、结论可靠。因此本文提出的理论均可用于指导生产设计。

Non-Newtonian viscous flow field calculation and extrusion behavior of the twin-screw extruder

In this dissertation, the twin screw intermeshing geometry is systematically analyzed according to the rolative motion principle. The relations among the geometric parameters of screw and the analytic of screw sections are derived, the formulas of calculating the aroa and volume of characteristic screw regions are deduced, and the relations between them and the geometric parameters of screw are discussed. Based on the results above, the principles of designing the geometric parameters of scrow are put forward from the gemotric point of view. To verify the validity of theory, the theoretical and experimontal results of intermeshing geometry are compared.

   Countering the special flow characters of the fluid and the complex of the flow field in twin screw extruder, the penalty finite element method (PFEM) and the boundary element method (BEM) are first adopted in this dissertation to solve the flow field in twin screw extruder after analyzing the defects of the traditional pressure-velocity finite element method in solving the similar flow field and a now method is proposed to handle the nonlinearity. It is proved by practical calculation that new methods above have many advantages (such as economy, convenience, high efficiency, high generality and reliability etc. ) in solving the complicated flow field.

   Based on analyzing the work done by predecssors, the physical and mathomatical models which are most close to practice up to now are established for the flow fields in the metering zone and venting zone of the intermeshing corotating twin screw extruder. By means of PFEM and BEM, the viscous flow fields in the metering zone and venting zone which are nonnewtonian, nonisothermal and include three directional velocities are solved in IBM-PC computer, according to the results of flow field calculation, the operating charaeteristic parameters are colculated, analyzed and discussed. After this, the Principles of selecting the technological parameters and designing the geometric parameters of screw are raised on the basis of the achievement above, in addition, the ways of solving the problems occuring in practice (such as how to restrain melt flooding from vent, improve the venting effect, restrain the fluctuation of operating characteristic parameters and so on) are pointed out.

   In this dissertation, the principles of scaling corotating twin screw extruder up and down are proposed on the basis of analyzing the similar conditions of the flow field in metering zone.

   The experimental results obtained in the laberatory and factories are compared with the theoretical results, it is proved that in this dissertation the models are resonable, the calculating methods are advanced and the conclusions are reliable, therefore, the theory established in this dissortation can be used to direct practice.